MANAMA, BAHRAIN — Common images of the U.S. Coast Guard's duties include boat rescues on the Great Lakes, pursuits of smugglers in the Caribbean and patrols of U.S. ports in the post-Sept. 11 security buildup.

But "Coasties" are also hip-deep in one of the world's riskiest and most politically volatile missions: boarding ships in the Persian Gulf to search for contraband, weaponry and suspected terrorists.

The danger of the boarding mission in one of the world's busiest waterways became clear when Iranian patrol boats seized 15 British sailors and marines who were searching a dhow suspected of smuggling automobiles. The Iranians held and interrogated the Britons for 13 days, ratcheting up tension between Tehran and the West.

As part of their pre-deployment training, Coast Guard personnel in this region have been schooled in boarding techniques at a facility in the United States run by the private security firm Blackwater USA. Besides conducting many of the boardings, the Coast Guard runs a training facility here for U.S. sailors.

In the last year 1,550 U.S. personnel have been trained here by the Coast Guard. A second and larger Coast Guard training facility, devoted largely to Iraqi sailors, is in the Iraqi port of Umm al Qasr. In deference to Islamic culture, none of the Coast Guard's female members are assigned to the Umm al Qasr facility.

Several Persian Gulf nations have sent their sailors to the Coast Guard for training. The British have their own training program.

The British military is investigating the March 23 seizure of the naval personnel and why the 15, although armed, did not resist. The report, led by a top officer with the Royal Marines, is expected to be completed soon.

Coast Guard members say that if the incident had happened to them, they would not have gone as passively as the British when the Iranians ordered them into their patrol boats.

"We would have had a use of force: bottom line," said Capt. Gary Smialek, commander of Coast Guard Task Force 55.6 in Bahrain.

At the facility here, sailors are taught how to scale the side of a ship, how to "clear" rooms and how to use an acetylene torch to cut into metal containers.

One exercise involves pop-up targets. Some are threatening, some not, and decisions on whether to shoot have to be made instantaneously.

"If we have people who can't decide between good and bad, that's not somebody you want on boarding teams," said Petty Officer 1st Class Dan Morales, an instructor and machinist's mate. "You have to separate the guilty from the sheep."

The Coast Guard keeps six Island-class patrol boats stationed in the gulf. At 110 feet in length, the cutters are the smallest of the U.S. vessels in the region but have the speed and shallow draft considered ideal for boarding missions.

For its training facilities and boats, the Coast Guard has 250 officers and enlisted personnel in Bahrain. Because of security concerns, their families remain in the United States.

The hot spot for boarding is in the northern reach of the gulf, near the boundary of Iranian territorial waters.

"Most of us are itching to get back north," said Petty Officer 1st Class Scott Titilah, lead instructor and boatswain's mate.

The tour of duty for Coast Guard personnel is a year, and most of them volunteer to go. After a year here, they return to the U.S. for icebreaking, drug interdiction, routine patrolling — far from the geopolitical spotlight of the Persian Gulf.

"In the Coast Guard, this is the place to be," said Lt. William Preston, head of training.